1. Field of the Invention
The present invention relates to a camera, and more particularly to a camera that is capable of both silver-halide shooting (recording of object images as pictures on silver-halide film) and video shooting (recording of object images as electronically reproducible moving and still pictures).
2. Description of the Prior Art
In general, video cameras are not capable of silver-halide shooting, and cameras based on silver-halide photography such as single-lens reflex cameras are not capable of video shooting. However, Japanese Laid-open Patent Application No. H1-133038 proposes a camera that is capable of both silver-halide shooting and video shooting. This camera, as shown in FIGS. 17A and 17B, is provided with a half mirror HM that can rotate 90.degree. to change its position, so that the light flux having passed through the taking lens (not shown) is split by the half mirror HM into a reflected light flux and a transmitted light flux.
When the half mirror HM is in the position shown in FIG. 17A, the light flux reflected therefrom enters an optical viewfinder system F, whereas the light flux transmitted therethrough enters a silver-halide shooting system G. As a result, it is possible to perform silver-halide shooting while observing the object through the optical viewfinder system F. In contrast, when the half mirror HM is in the position shown in FIG. 17B, the light flux reflected therefrom enters a video shooting system V, whereas the light flux transmitted therethrough enters the silver-halide shooting system G. As a result, it is possible to perform both video shooting and silver-halide shooting while observing the object through an electronic viewfinder (not shown) incorporated in the video shooting system V. In this way, to achieve compatibility between silver-halide shooting and video shooting, the camera proposed in Japanese Laid-open Patent Application No. H1-133038 relies on the use of the half mirror HM, whose semitransparency makes it possible to split a light flux and whose rotation makes it possible to switch optical paths.
A disadvantage of the above-mentioned camera is that it does not allow free placement of a distance measurement device. In ordinary single-lens reflex cameras, a distance measurement device, which is essential to realize automatic focusing (AF), is placed above or below a mirror box. However, in the arrangement shown in FIGS. 17A and 17B, where the half mirror HM is rotatable, it is impractical to place the distance measurement device above or below the mirror box, because the presence of a drive mechanism for rotating the half mirror HM imposes various restrictions on the placement of the distance measurement device and of an AF mirror (which is needed to direct light to the distance measurement device), and because the driving of the AF mirror in such a situation requires a complex mechanism. Instead, if the distance measurement device is placed by the side of the mirror box, then the retraction of the AF mirror requires a complex mechanism and, in addition, it is difficult to secure space for the retracting motion of the AF mirror.
Another disadvantage of the above-mentioned camera is that it requires a relatively large mirror box. Ordinarily, single-lens reflex cameras are provided with a swing-up mirror with which to reflect totally the light flux having passed through the taking lens toward the viewfinder system. Usually, a small swing-up mirror will suffice for ordinary single-lens reflex cameras, since it is not necessary to use a large mirror simply to reflect the light flux toward the viewfinder. However, in the arrangement shown in FIG. 17A and 17B, where the light flux transmitted through the half mirror HM is used by the silver-halide shooting system G, a considerably large half mirror HM is required. This is because an unduly small half mirror HM may cause eclipse in the light flux directed to the silver-halide shooting system G, especially when a large-aperture interchangeable lens is used. Since the half mirror HM is rotated to switch optical paths, a larger half mirror HM requires a larger mirror box, which inevitably makes the camera as a whole accordingly larger.